Conventional lawn mowers, be they walk behind, lawn tractors and riders of all types, have long had the disadvantage of an inability to closely trim or edge around stationary objects such as trees, posts, buildings and the like. Commonly, the trimming and edging is accomplished by hand, using a string trimmer or trimming mower. Such hand edging is time consuming and physically demanding.
Particularly troublesome areas to mow are found in cemeteries. When mowing a cemetery, one has to mow around a multitude of permanent grave stones without damaging the stones. Typically, the job is completed with a string trimmer by hand. Stone placement and size differ throughout cemeteries thus creating a great deal of hand labor to properly mow and trim a cemetery.
A trim mower attachment for riding mowers is shown in U.S. Pat. No. 5,598,689, however, the trim attachment is fixed in place with respect to the horizontal cut of the mower deck and is hinged to move in the vertical plane to provide compensation for the changing contours of the mowing surface. The structure provided in the ""689 patent is seriously deficient however in assisting the mower operator to closely trim around a large number of fixed obstacles such as cemetery stones and fence posts. In fact, the extent with which the trimmer is positioned outside the normal width of the mower deck forces the operator to exercise careful diligence when approaching stationary objects or risk damaging the mower.
Another trim mower attachment is disclosed in my copending patent application Ser. No. 09/641,048, filed Aug. 17, 2000 now U.S. Pat. No. 6,546,706 Apr. 15, 2003. The mower deck and trimmer combination disclosed in my patent application maintains a trimming apparatus to one side and forward of the mower deck. The trimmer is engaged to the mower deck by a pivot member defining a fixed pivot axis normal to the cutting plane of the mower deck. When the trimmer encounters an obstacle, it moves horizontally about the fixed pivot axis. The teachings of the ""048 application are specifically incorporated herein by reference.
It has been discovered that, under certain operating conditions, the trimming head encounters difficulty in moving about the fixed pivot axis. For instance, if the trimming head encounters a rough surface the head has a tendency to become unstable and xe2x80x9cdancexe2x80x9d. Also, if the trimming head moves past an obstacle and the operator reverses the drive of the apparatus, the trimming head may not move about the pivot axis properly, thus resulting in potential damage to the trimming head and mower deck.
Thus it is an object of this invention to provide a trimming head having two ranges of motion which create a natural rotation of the head while the head moves about an obstacle.
It is a further object of this invention to provide a mower deck having a rotating trimming head in combination therewith which provides a capability of trimming around stationary objects such as fences, posts, trees, walls, guard rails and the like.
Yet another object of this invention is to provide a mower deck with a rotating trimming head that flexes vertically to follow the contour of the mowing surface.
The invention provides an improved trimmer structure for use with mower decks wherein the trimmer is resiliently positioned with respect to the mower deck to have an overlapping cutting path to the cutting path of the mower deck. The trimming head includes a rotating housing which is designed to rotate about the shaft of the cutting blade. The trimmer is connected to an arm fixed to the mower deck and rotates on a fixed pivot axis normal to the cutting plane of the mower deck when encountering fixed obstacles. A resilient member maintains the trimmer in an extended position away from the mower deck, allows the trimmer to move to a retracted position adjacent the mower deck when it contacts a fixed obstacle and returns the trimmer to its extended position after the obstacle has passed. A drive for operating the trimmer is adapted to move with the trimmer. Rotation of the trimming head housing eliminates frictional interference between the trimming head and obstacle, thereby facilitating the natural tendency of the trimming head to rotate as it moves around obstacles, whether in the forward direction or the reverse direction. The rotating trimming head also flexes vertically to allow the trimmer to follow the contour of the moving surface.
As a result, an operator may mow in a straight line and trim around stationary obstacles and reverse drive without interfering with the operation of the mower deck.